According to conventional philosophies, pneumatic rubber tire outers are made exclusively of a relatively hard durable solid rubber. However, the characteristics of relatively hard non-sponge (“solid”) rubber do not favorably support the special needs of certain sports vehicles, such as mountain bikes, bicycle motorcross (“bmx”) vehicles, cross-country bicycles, All Terrain Vehicles (“ATV”), and go-carts. Similarly, the characteristics of relatively hard solid rubber do not favorably support the needs of certain other types of special vehicles, including for example, wheelchairs, baby joggers, skateboards, rollerblades, scooters, motorcross vehicles, and others.
Pneumatic mountain bicycle tire outers have conventionally been made with relatively hard durable solid rubber. Relatively hard durable solid rubber is used in making the outers for such tires under the conventional thinking that because a mountain biking tire is subjected to high-friction conditions, the characteristics of relatively hard durable solid rubber will provide long wear.
There are a number of problems, however, with such tires. For example, relatively hard solid rubber does not have a high-friction coefficient—in most cases, the harder the rubber, the lower the friction coefficient of the rubber. Therefore, most conventional relatively hard solid rubber tires do not provide good traction characteristics.
Another problem with pneumatic tires made with relatively hard solid rubber outers is that they do not exhibit good shock absorption characteristics. In the case of mountain bikes, shock absorption is a critical factor in the design of such bikes. Mountain bikes can cost ten times the amount of a regular street bicycle—much of the cost being devoted to providing highly-advanced shock absorption characteristics to various structural features of the bicycle. After spending thousands of dollars on a highly-advanced shock absorbing bike frame, the mountain biker then mounts pneumatic tires made of relatively hard solid rubber that characteristically exhibit low shock-dampening characteristics—that is, they bounce.
Soft rubber exhibits higher-friction coefficient characteristics than harder rubber. However, soft rubber does not wear well and further does not exhibit significantly reduced dampening characteristics as compared to harder rubber.
Sponge rubber exhibits high-dampening and high-friction coefficient characteristics. However, a sponge rubber made using very soft rubber would not exhibit durability characteristics necessary for pneumatic tires.
As with pneumatic tire rubber outers, rubber outers, that is, an outer layer of rubber, in other applications that are often subjected to high-wear, high-friction conditions, such as, for example, shoe sole outers, are often made with relatively hard durable solid rubber according to the conventional thinking that the relatively hard durable solid rubber will provide long wear. However, as with tires, shoe sole outers (outsoles) and other rubber outers made according to this conventional thinking do not exhibit high-friction coefficient or shock-absorbing characteristics.